FIGS. 1 and 2 illustrate a method of punching a product in a predetermined shape from a template, and more particularly illustrate utilizing a press 101 to punch a template made of aluminum to form a base plate of a tape cassette. In FIG. 1, the press 101 includes a punch 102 and a die 103. In this method of punching the template, the template 104 is placed on the die 103 and the punch 102, applied to an upper surface 104a of the template 104, thereby forming a base plate 105.
This method of punching a template of FIG. 1 has been found to be disadvantageous as a result of forming the template 104 by a single punching operation, that is, the punch 102 is only applied to the upper surface 104a of the template 104.
As is shown in FIG. 2, in the base plate 105 punched from the template 104 by the punching operation of FIG. 1, a portion of the punched end surface 111 thereof connected with the upper surface 104a of the template 104 forms a shear plane 111a, and a portion of the punched end surface 111 connected with a lower surface 104b of the template 104 forms a fracture plane 111b. The shear plane 111a is brought into a so-called cut state by the punch 102, so as to be a smooth surface. On the other hand, the fracture plane 111b is brought into a so-called torn state, so as to become a coarse surface, and a punched flash 111c is formed in an end of the fracture plane 111b when it is torn off.
On the other hand, in a punched end surface 112 of the base plate 105 formed by punching the above-mentioned template 104 by the punching operation of FIG. 1, a portion of the punched end surface 112 connected with an upper surface 105a of the base plate 105 forms a shear plane 112a. Moreover, a portion of the punched end surface 112 connected with a lower surface 105b of the base plate 105 forms a fracture plane 112b. As a result of this punching operation, a punched flash 112c is formed in the fracture plane 112b, similar to the punched flash 111c in the punched end surface 111 of the template 104.
The punched flash 111c formed in the above-mentioned template 104 does not present a significant problem. However, the punched flash 112c in the base plate 105 can cause a person handling the base plate 105 to be injured, for example. Further, when a tape cassette is manufactured which incorporates the base plate 105, the punched flash 112c may damage hardware, i.e., a drive.
In order to alleviate the adverse effects of the above-mentioned punched flash 112c, a method of crushing the flash 112c by a punch 121, has been developed, as shown in FIGS. 3 through 5. In this method, however, the cost of the base plate is increased because the number of steps necessary to manufacture the base plate is increased. Further, there is a danger in the method of FIGS. 3 through 5 that the punched flash 112c can be stripped or dropped because the punched flash 112c is only crushed and is not removed.
For the foregoing reasons, it has been found desirable to provide a method for punching a template which prevents formation of such a punched flash.